1. Field of the Invention
This invention relates to a ferrite magnetic powder including an alkaline-earth metal constituent, more specifically to a ferrite magnetic powder for bond magnet that experiences only small decrease in coercivity when molded into a bond magnet.
2. Background Art
In order to obtain a bond magnet molded of ferrite magnetic powder and binder that has high magnetic force, it is necessary to increase the ferrite magnetic powder filling factor. JP-Hei9-106904A (Reference) teaches that a bond magnet molded using a ferrite magnetic powder at a filling factor with respect to the binder of 93 wt % achieves (BH) max of 2.5MGOe or greater.
Moreover, high magnetic force bond magnets are used in audio-video and office automation equipment, small motors employed in automotive and other electrical components, magnet rolls of copying machines and various other applications in which low-temperature demagnetization is a problem, so that maintenance of high coercivity is desirable.
Although, as taught by Reference, the filling factor with respect to the binder can be increased to achieve high magnetic force by appropriately blending fine and coarse powders, the coercivity is liable to decrease when the filling factor is increased too far. Reference points out that high fluidity is maintained and a molded product having high (BH)max can be obtained even when the filling factor is increased. However, it does not offer any useful teaching regarding how to prevent decrease in coercivity (iHc) when the filling factor is increased.